I found a yellow spot on my chickens egg

[MysteryChicken]

Yes that could very much be it. Thats the most likely reason

It's the most possible reason I can think of. I've had quite a few of these eggs.

 

[aart]

Would this egg with the yellow have been laid around the same time as the egg with the hole in it? If so, it could easily have been that. That egg could've left behind a little yoke or been carried into the nesting box on the feathers or legs of a hen.

This^^^

Chicken poop is not yellow, that is yolk carried into nest.